Finite strip method for the free vibration and buckling analysis of plates with abrupt changes in thickness and complex support conditions

The free vibration problem of a stepped plate supported on non-homogeneous Winkler elastic foundation with elastically mounted masses is formulated based on Hamilton's principle. The stepped plate is modelled by finite strip method. To overcome the problem of excessive continuity of common beam vibration functions at the location of abrupt change of plate thickness, a set of C¹ continuous functions have been chosen as the longitudinal interpolation functions in the finite strip analysis. The C¹ continuous functions are obtained by augmenting the relevant beam vibration modes with piecewise cubic polynomials. As these displacement functions are built up from beam vibration modes with appropriate corrections, they possess both the advantages of fast convergence of harmonic functions as well as the appropriate order of continuity. The method is further extended to the buckling analysis of rectangular stepped plates. Numerical results also show that the method is versatile, efficient and accurate.     

Diurnal thermal cycling effects on microwave signatures of thin seaice

To investigate effects of diurnal thermal cycles on C-band polarimetric backscatter and millimeter-wave emission from sea ice, the authors carried out a winter experiment at the outdoor geophysical research facility (GRF) in the cold regions research and engineering laboratory (CRREL), the ice sheet grew from open sea water to a thickness of 10 cm in 2.5 days, during which they took polarimetric backscatter data with a C-band scatterometer, interlaced with brightness temperature measurements at 90 GHz in conjunction with meteorological and sea ice characterizations. The initial ice growth in the late morning was slow due to high insolation. As the air temperature dropped during the night, the growth rate increased significantly. Air temperature changed drastically from about -12 to -36°C between day and night, the diurnal thermal cycle repeated itself the next day and the growth rate varied in the same manner. Ice temperature profiles clearly show the diurnal response in the ice sheet with a lag of 2.5 h behind the time of the maximum short-wave incident solar radiation. The diurnal cycles are also evident in the millimeter-wave brightness temperature data, measured sea ice backscatter revealed substantial diurnal variations up to 6 dB with repeatable cycles in synchronization with the temperature cycles and the brightness temperature modulations, the diurnal cycles in backscatter indicate that the dominant scattering mechanism related to thermodynamic processes in sea ice is reversible, a diurnal backscatter model based on sea ice electrodynamics and thermodynamics explains the observed diurnal signature. This work shows that diurnal effects are important for inversion algorithms to retrieve sea ice geophysical parameters from remote sensing data acquired with a satellite synthetic aperture radar (SAR) or scatterometer on Sun-synchronous orbits     

Creep and shrinkage analysis of reinforced concrete frames by history‐adjusted and shrinkage‐adjusted elasticity moduli

Consideration of the time‐dependent deformations due to creep and shrinkage is often necessary to ensure satisfactory behavior of complex concrete structures. The stresses and deformations of a reinforced concrete frame can be analyzed by the finite element method using time integration. However, as the full stress history prior to each time interval considered is necessary, with the increase in the number of time intervals used, the amount of computations increases dramatically. The concept of age‐adjusted elasticity modulus is further explored to develop new functions for efficient evaluation of time‐dependent behavior of concrete frames. The history‐adjusted elasticity modulus is devised so that stage construction can be modeled more accurately. Likewise, the shrinkage‐adjusted elasticity modulus is introduced to enable shrinkage analysis to be carried out using one single step. The methods can cope with frame structures built and loaded in several stages. Accurate results can be obtained by considering just a few large time intervals instead of those fine time steps used in time integration. Numerical examples are presented to demonstrate the usefulness of the new methods. Copyright © 2007 John Wiley & Sons, Ltd.     

Biomonitoring using accessible human cells for exposure and health risk assessment

We describe a nonradioactive preembedding in situ hybridization protocol using digoxigenin-labeled RNA probes and tyramide signal amplification to increase the sensitivity of detection. The protocol is sensitive enough for electron microscopic localization of endogenous messenger RNAs encoding beta-actin and amphoterin. Three visualization methods were compared: diaminobenzidine enhanced by nickel, Nanogold enhanced by silver and gold toning, and fluorescently labeled tyramides. Diaminobenzidine and Nanogold can be used in both light and electron microscopy. The nickel-enhanced diaminobenzidine was the most sensitive visualization method. It is easy to accomplish but a drawback is poor spatial resolution, which restricts its use at high magnifications. Nanogold visualization has considerably better spatial resolution and is therefore recommended for electron microscopy. Fluorescent tyramides, especially TRITC-tyramide, offer a good detection method for fluorescence and confocal microscopy. The methods were used to localize amphoterin and beta-actin mRNAs in motile cells. Both mRNAs were found in the soma and cell processes. In double labeling experiments, beta-actin mRNA localized to filamentous structures that also contained ribosomal proteins. Especially in the cortical cytoplasm, beta-actin mRNA was associated with actin filaments. Direct localization to microtubules was only rarely seen. (J Histochem Cytochem 47:99-112, 1999)     

Process Capability Improvement for Multistage Processes

While the quality control procedures for multistage has been considerably studied, multistage process capability analysis has not been explored much at all. Fostering on the recent development of the multistage process variation transmission model, a multistage process capability analysis algorithm is developed to prioritize process improvement efforts. The application of algorithm is demonstrated with two 2-stage industrial process examples and a 4-stage process example for its expandability.     

Efficient visualization of large routing topologies

As the Internet grows in size and complexity, network managers face a significant challenge in trying to understand the behaviour of routing protocols in large networks. In this paper, we present a tool called VLNT (visualizing large network topologies), which helps network managers to analyse complex routing topologies. A key contribution of our system is a novel hybrid layout algorithm, which significantly reduces the computation time required to layout large network topologies in comparison to conventional layout approaches. In addition our algorithm includes a novel termination criterion that avoids unnecessary iterations when optimizing the network layout. We demonstrate how the visualization features of VLNT can be used to analyse and improve BGP routing topologies, and provide examples using real‐life routing data. Copyright © 2004 John Wiley & Sons, Ltd.     

Computationally-efficient phased-mission reliability analysis forsystems with variable configurations

Several techniques and a software tool for reliability analyses that generally apply to fault-tolerant systems operating in phased-missions are given. Efficient models, using Markov chains without an explosion of the state space, are provided for missions consisting of multiple phases, during which the system configuration or success criteria can change. In different phases, the failure rates and the fault and error handling models can also change, and the duration of any phase can use deterministic or random models. An efficient reconfiguration procedure that is computationally more efficient than any existing technique is developed. The technique is demonstrated using a numerical example to show the effects of mission phases on the system reliability     

Evaluations of P/M Gamma Titanium Aluminides

For the last five years, the Structures, Materials and Propulsion Laboratory of the Institute for Aerospace Research, National Research Council of Canada, has devoted a significant amount of effort investigating powder metallurgy gamma titanium aluminides. The main results of the studies on microstructural evolution, hot workability, creep behaviour and microstructure-mechanical property relationships for P/M gamma alloys are reviewed in this article. Work is in progress to apply the knowledge gained to cast gamma alloys for gas turbine applications.     

NO Reduction with Hydrogen over Cobalt Molybdenum Nitride and Molybdenum Nitride: A Comparison Study

Cobalt molybdenum nitride (Co₃Mo₃N) and molybdenum nitride (Mo₂N) were investigated for the catalytic reduction of NO with H₂. The latter deactivated rapidly with time on stream, whereas the former remained active and stable over a test period of 30 h. The results of X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and H₂-temprature-programmed reduction (H₂-TPR) characterization indicated that the deactivation of Mo₂N was due to the bulk oxidation of Mo₂N to MoO₂. As for the Co₃Mo₃N catalyst, despite partial decomposition into Mo₂N and Co, it remained resistant to oxidation. The results suggest that compared to the monometallic nitride, the bimetallic one is more suitable for NO reduction with H₂.